Absorbent article with high stiffness

ABSTRACT

The invention relates to an absorbent article such as a sanitary napkin, an incontinence guard, or a panty-liner, which article has a generally elongated shape with a longitudinal direction and a transverse direction and exhibits two side edges (9, 10), two end portions (6, 7), and a crotch portion (8) located between the end portions (6, 7), which article further exhibits a liquid-pervious cover layer (2), intended to be facing the user during use, and a liquid-impervious cover layer (3), intended to be facing away from the user during use. The article comprises at least within the crotch portion (8) a stiffening element (15) of a material with a very high intrinsic stiffness, whereby the article in the crotch portion (8) has an extension in the transverse direction which during use of the article is between 40 mm and 15 mm and preferably is between 20 mm and 35 mm.

TECHNICAL FIELD

The invention relates to an absorbent article such as a sanitary napkin,an incontinence guard, or a panty-liner, which article has a generallyelongated shape with a longitudinal direction and a transverse directionand also exhibits two side edges, two end edges, two end portions, andalso a crotch portion located between the end portions, which articlefurther exhibits a liquid-pervious cover layer, intended to be facingthe user during use, and also a liquid-impervious cover layer, intendedto be facing away from the user during use.

BACKGROUND OF THE INVENTION

When using an absorbent article such as a sanitary napkin, anincontinence guard or the like, with a relatively small size andintended to principally be able to be accommodated in the crotch regionof a user, it is a significant problem that the article during use isdeformed by the forces which arise for example when the user movesabout. Since the article is subjected to compression between the legs ofthe user, creases and ruptures arise in an uncontrolled manner in theabsorbent body of the article as well as in its liquid-pervious coverlayer. This is of course a disadvantage, since wrinkles act asliquid-conducting channels, in which liquid may flow out over the edgesof the article. Furthermore, ruptures in an absorbent body lead todeterioration of the liquid-distributing ability in the absorbent body,so that the liquid stays in the acquisition region of the article, i.e.in the region which first is wetted by the liquid. Thereby, the risk ofthe acquisition region being supersaturated by liquid is imminent,entailing an increased risk of leakage.

There is also a significant risk that the side edges of the articleduring use are folded in over the liquid-pervious surface, so that theportion of the article which is directly accessible for reception andabsorption of liquid is considerably reduced. Also deformation of thistype increases the risk of leakage.

Another significant problem associated with the fact that an absorbentarticle is deformed during use, is that the article becomes wrinkled andlumpy and feels uncomfortable to wear. At worst, sharp and chafingcreases are formed which irritate the skin of the user during use.

In U.S. Pat. No. 4,217,901 a sanitary napkin comprising a compressedlayer of fluff pulp is disclosed, which layer serves to increase theresistance towards deformation of the sanitary napkin. Unfortunately, afluff pulp layer loses its stiffness when wetted, whereby the previouslyknown sanitary napkin only exhibits an elevated stiffness in an initialstage of use. Furthermore, a loosening of the compressed fluff pulplayer takes place during use, depending on the fact that the fibres ofthe layer are torn apart when the sanitary napkin is subjected totension and pressure forces during use. A further disadvantage with thepreviously known compressed fluff pulp layer is that it substantiallylacks resilience, which implies that a layer that has been cracked orotherwise deformed does not have the ability to regain its originalshape.

SUMMARY OF THE INVENTION

By means of the present invention an article of the type discussed inthe introduction has been achieved, in which the disadvantages andproblems which are associated with such previously known articles havebeen essentially eliminated. An article designed in accordance with theinvention is thereby mainly characterized in that the article, at leastwithin the crotch portion, comprises a stiffening element of a materialwith a very high intrinsic stiffness, whereby the article within atleast a part of the crotch portion has a dimension in the transversedirection which, when the article is used, is between 15 mm and 40 mmand preferably is between 20 mm and 35 mm.

Since the article comprises a component with a very high stiffness, therisk of uncontrolled deformation by means of transverse compression hasbeen completely eliminated. The article according to the inventionprimarily has the ability to resist compression when it is subjected tothe forces which arise between the legs of the user during use.

According to a preferred embodiment of the invention, the stiffeningelement can only be compressed to approx. 80% of its original widthduring compression of the crotch region in the transverse direction ofthe article with forces of the magnitude which are present during use.

Measurements have shown that all humans have a critical area in thegroin portion between two muscle groups which extend from the inside ofthe pelvis bottom down along each thigh. The distance between the twomuscle groups has thereby been found to be surprisingly similar for allhumans, independently of body shape and weight. Thus, the distancebetween the thighs of a user is of course affected by fatness, while thedistance between the muscle groups in the crotch of the user is thesame, independently of whether the user is thin, of normal weight oroverweight. It was shown that the factor which decides if a userexperiences discomfort in the form of pressure or chafing against theinsides of the thighs is whether the absorbent article during use has awidth which in the critical area considerably exceeds the distancebetween the muscle groups in the groin area. This distance has beenfound to be between approx. 30 mm and 35 mm, Furthermore, it has beenprovided that an article with a width which during use exceeds 40 mm inthe critical area is perceived as uncomfortable by the majority ofusers. On the contrary, it is seldom perceived to be unpleasant that anabsorbent article presses against or displaces fatty tissue which mayoccur in the crotch area.

In the case of conventional deformable absorbent articles, the limitedspace in the crotch region of the user entails that the articles arecompressed in an uncontrolled way between the legs of the user and arecreased in order to be accommodated in the groin area. Where anabsorbent article according to the invention is concerned, having a verystiff shape-retaining element in the crotch portion, compressing mayonly take place to a limited extent, whereby the degree of possiblecompression is controlled by the design of the stiff crotch portion. Itis therefore essential that the width of the absorbent article in thecrotch portion during use does not exceed the critical value which canbe tolerated by the user.

Thereby, however, it is not necessary that the crotch portion along itsentire length has a width which during use is below 40 mm. Since thecritical area in the crotch region of the user is approx. 5 mm to 15 mmlong, it is sufficient if the part of the crotch portion which isintended to be arranged within this area during use fulfils therequirement of a maximum width. Accordingly, it is sufficient for theinvention if, in the longitudinal direction of the article, there is a5-15 mm long area in the crotch potion within which the width during useof the article is not greater than approx. 40 mm and preferably is notgreater than approx. 35 mm.

A suitable stiffening element is profiled in the transverse direction ofthe article and exhibits at least one longitudinally extending ridge, orfurrow. Thereby, a longitudinal ridge with rounded surface may bearranged along each side edge of the article at least at the crotchportion. An absorbent article according to the invention isadvantageously provided with a centrally arranged longitudinal hump.Thereby, a longitudinal furrow may be arranged at each side of thecentral hump, between this and the side edges of the article.Advantageously, longitudinal ridges are combined with lowered portions,or furrows.

Furthermore, transverse compression of the article in the vicinity ofthe transition area between the crotch portion and the front portionaffects the stiffness of the article during use. Such compressionincreases the beam effect rendered by the stiffening element andcounteracts bending of the front portion in relation to the crotchportion.

Thus, the stiffness of an absorbent article depends to a high degree onthe shape of the article, particularly the shape of the stiffeningelement. Consequently, a stiffening element with beams in the form ofridges or furrows has a higher stiffness, perpendicularly to theextension of the ridges or the furrows, than a completely flat material.The beams may be obtained by forming the material itself, or byreinforcing it with strips or ribs of a separate material. Furthermore,the stiffness and the resistance to bending and twisting may beincreased by imparting a bowl-shape to the material, or by means ofincreased material thickness.

As examples of plastic materials which have been found to havesufficient bending stiffness and torsional rigidity in order to achievethe ability to resist uncontrolled deformation which is necessary forthe invention, polyethylene or polypropylene with a layer thickness ofat least 0,4 mm may be mentioned. Furthermore, it is possible toincrease the stiffness of a plastic layer by mixing the plastic withtalc, chalk, or other stiffness-increasing fillers. The materialstiffness of a plastic film which is suitable for use as a stiffeningelement in an article according to the invention should thereby exceed100 N, measured in accordance with ASTM D 4032-82 “Circular BendProcedure”, which method is described in detail in EP 0 336 578. In thiscontext, material stiffness refers to the stiffness of a flat materiallayer.

Furthermore, it is possible to use plates, rods, skeleton-likeconstructions or the like of metal, wood or other stiff materials whichdo not substantially change their stiffness properties when wetted, andare not broken by the forces which arise during use of an absorbentarticle. Accordingly, it is possible to use, for instance, cardboardwhich has been treated in order to resist wetting for example by meansof coating with plastic or the like in order to prevent that thematerial softens when wetted and in order to increase the toughness ofthe material and to reduce the risk of breaking. It is not completelyessential for the invention that the stiffening element is constitutedby a continuous material layer, but stiffening elements composed offstiff beams, tubes, pegs, or the like may also be used. A stiffeningelement which thereby has been found to perform particularly well is askeleton-like structure of bent metal rods. On condition that such astructure conforms well to the anatomy of the user and, particularly,does not exceed the critical width in the crotch region of an absorbentarticle, such a metal skeleton maybe allowed to be completelyincompressible by such forces which occur during normal use.

When very rigid stiffening elements are used it may be desirable toarrange soft, easily deformable edge portions on both sides along theside edges of the article. Such an arrangement allows for a certainamount of compression of the article in the transverse direction and, atthe same time, provides the article with soft, comfortable edges.

An anatomically designed article according to the invention is keptsecurely and comfortably in position against the body of the user duringuse, without the need for special attachment means. This implies thatthe article is completely unattached to the panties of the user, wherebythe risk that the article during use moves with the panties and therebyends up in an incorrect position in relation to the body of the user isalmost completely eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will in the following be described in greater detail withreference to the embodiments which are shown in the attached drawings,Thereby:

FIG. 1 shows a sanitary napkin according to the invention,

FIG. 2 shows a section along the line II—II through the sanitary napkinin FIG. 1,

FIG. 3 shows a section along the line III—III through the sanitarynapkin in FIG. 1,

FIG. 4 shows a sanitary napkin according to an alternative embodiment ofthe invention,

FIG. 5 shows a section along the line V—V through the sanitary napkin inFIG. 4 and

FIG. 6, shows a section along the line VI—VI through the sanitary napkinin FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The sanitary napkin 1, shown in FIGS. 1, 2 and 3, comprises aliquid-pervious cover layer 2, arranged on the side of the sanitarynapkin 1 which during use is intended to be facing the user, aliquid-impervious cover layer 3, arranged on the side of the sanitarynapkin 1 which during use is intended to be facing away from the user,and an absorbent body 4, enclosed between the two cover layers 2, 3.

The material of the liquid-pervious cover layer 2 may be, for example, aperforated plastic film, a plastic scrim or a textile material, anonwoven material or a laminate of, for example, a perforated plasticlayer and a nonwoven layer. The plastic is typically a thermoplastic,such as polyethylene or polypropylene. The expression nonwoven materialrefers to a non-woven fibre fabric. Suitable nonwoven materials mayconsist of natural fibres such as cellulose or cotton, or syntheticfibres such as polyethylene, polypropylene, polyester, polyurethane,nylon or regenerated cellulose, Naturally, it is also possible to usenonwoven materials made from fibre blends.

The liquid-pervious cover layer 2 shall receive and conduct the liquidinto the absorbent body 4. Furthermore, the cover layer 2 should be softand pleasant against the body of the user, and also be able to preventso-called rewetting, i.e. that absorbed body exudate forces its way backtowards the sin of the user. For reasons of comfort, and in order toavoid skin irritation, it is important that the surface on the part ofthe sanitary napkin which is in contact with the skin of the user ismaintained as dry as possible during use. Furthermore, a dry surface onthe sanitary napkin is perceived by the user as being cooler and morepleasant during use, and is both from a purely visual point of view andwhen handling the sanitary napkin when this is to be replaced, morepleasant than a soiled, wet surface.

It is not necessary for all embodiments of the invention that theliquid-pervious cover layer 2 in fact is constituted by a separatematerial layer. The liquid-pervious cover layer may, for instance,constitute an integral part of an absorbent body. Consequently, it isconceivable to exclude the liquid-pervious cover layer when theabsorbent body comprises an absorbent foam layer. Furthermore, anabsorbent nonwoven material may be utilized, which may be an integralcomponent of an absorbent body and at the same time constitute aliquid-pervious cover layer.

The liquid-impervious cover layer 3 consists of a liquid-impermeablematerial. Thin, liquid-impervious plastic films are suitable for thepurpose. However, it is also possible to use materials which areliquid-pervious to start with, but which have been furnished with acoating of plastic, resin, or other liquid-impervious material. Thereby,leakage of liquid from the bottom side of the absorbent article isprevented. The liquid-impervious cover layer 3 may, accordingly, consistof any material which is skin-friendly and fulfils the criteria ofliquid-impermeability. Examples of materials which are suitable asbarrier layers are plastic films, nonwoven materials and different typesof laminates. Useful plastic films are, for example, those which consistof polyethylene, polypropylene, or polyester. Optionally, theliquid-impervious cover layer 3 may consist of a laminate of aliquid-impermeable plastic layer facing the absorbent body, and anonwoven layer facing the underclothing of the user. Such a constructionprovides a leakage-proof barrier layer with a textile feel. As is thecase with the liquid-pervious cover layer 2, it is not necessary thatthe liquid-impervious cover layer 3 is constituted by a separate layer.Accordingly, it is conceivable that the liquid-impervious cover layer 3constitutes an integral part of an absorbent material, for instance anabsorbent foam layer with a liquid-impervious surface.

The absorbent body 4 may advantageously be constituted primarily bycellulose fluff pulp. This may be provided in the form of reels, balesor sheets which are dry shredded and in a fluffed state are transformedinto a pulp mat, with or without the addition of so-calledsuper-absorbents, which are polymers with the ability to absorb severaltimes their own weight of water or body exudate. Examples of otheruseful materials are different types of natural fibres, such as cottonfibres, peat, or the like. It is, of course, also possible to utilizeabsorbent synthetic fibres, or blends of natural fibers and syntheticfibres. The absorption material may, furthermore, include additionalcomponents, such as liquid-distributing members or binders such as, forexample, thermoplastic fibres which have been heat-treated in order toretain short fibres and particles as a coherent unit. It is alsopossible to utilize different types of absorbent foam material in theabsorbent body 4.

The two cover layers 2, 3 are mutually connected outside the absorbentbody 4 and form a protruding edge 5 around the entire periphery of thesanitary napkin. The joining the cover layers may be performed in anysuitable way, for instance, by means of gluing, sewing, or welding withheat or ultrasonically.

The sanitary napkin 1 is substantially hourglass-shaped and therebyexhibits a front portion 6, intended to be turned forwards on the userduring use, a rear portion 7, intended to be turned backwards on theuser during use, and an intermediate, narrower crotch portion 8,intended to be applied in the grown area of the user. Furthermore, thesanitary napkin 1 has two concavely curved side edges 9, 10, a convexlycurved front edge 11, and also a similarly convexly curved rear edge 12,

The partition of the sanitary napkin into a front portion 6, a rearportion 7, and a crotch portion 8, should not be understood as if sharplimits exist between the different portions 6-8, but is primarilyintended to facilitate the description of the sanitary napkin, startingfrom the differences which are present between the different portions6-8 depending on how they are intended to be placed in relation to thebody of a user. Thus, the transition between the different portions 6-8does not take place at predetermined transverse lines, but rather withintransition regions situated at a distance of approximately one third ofthe length of the sanitary napkin from the front edge 11 and the rearedge 12 of the sanitary napkin, respectively. Accordingly, the crotchportion 8 constitutes the part of the sanitary napkin which during useis intended to receive and absorb the main part of the liquid which issecreted to the sanitary napkin during use.

A stiffening element 15, for instance made of a rigid plastic layer, ora rigid metal plate, is arranged between the liquid-impervious coverlayer 3 of the sanitary napkin 1 and the absorbent body 4, and extendsacross the front portion 6 and the crotch portion 8 of the sanitarynapkin.

The stiffening element 15 is shaped as a spoon, or scoop, with a cuppedpart 16 situated at the front portion 6 of the sanitary napkin and arectangular flat part 17 situated at the crotch portion 8. The cuppedpart 16 of the stiffening element 15 has substantially the same shape inthe plane as the front portion 6 of the sanitary napkin, but is slightlysmaller. Thereby, the parts of the front portion 6 which project pastthe edge 19 of the stiffening element 15 form a soft, cushioning edgeregion 18, which partly serves as a leakage seal, and partly counteractschafing. In a corresponding way, the flat part 17 of the shape element15 does not extend all the way out to the side edge 9, 10 of thesanitary napkin in the crotch portion 8, but a narrow, soft andresilient edge region 18, consisting of parts of the two cover layers 2,3 and the absorbent body 4, extends between each respective side edgeand the corresponding side edges 20, 21 on the stiffening element 15.

The cupped part 16 of the stiffening element 15 is angled in thelongitudinal direction of the sanitary napkin in relation to the flatpart 17, whereby also the front portion 6 of the sanitary napkin 1 isangled in relation to the crotch portion 8, as is best observed in FIG.2. In order to obtain the desired angle of the sanitary napkin, thestiffening element 15 has been permanently curved, or bent along atransverse folding line 22, which is slightly curved in a directiontowards the front edge of the sanitary napkin. The angle α, between thesubstantially flat crotch portion 8 of the sanitary napkin and the frontportion 6 which is raised up from this, is thereby approximately 20°-50°and preferably approximately 30°. In FIG. 2, the angle α has beenindicated on the outside of the sanitary napkin, i.e. the side of thesanitary napkin which in use is intended to be facing away from theuser. The relevant angle is, however, in fact the angle on the inside ofthe sanitary napkin, since it is the inside which should conform to theanatomy of the user. In the shown example, it is of no importance if theangle is measured at the outside or the inside, since the value obtainedwill be the same, since both the front portion 6 and the crotch portion8 have the same inclination on the inside as on the outside.

The curved folding line 22 contributes to providing the sanitary napkinwith good shape stability and increases the bending stiffness of thestiffening element 15 at the folding line 22, since folding take placemore easily along a straight line than along a curved line. Thereby, theangle between the cupped part 16 of the stiffening element 15 and itsflat part 17 is maintained also when the sanitary napkin during use issubjected to force action. Furthermore, the folding line provides thefront portion 6 of the sanitary napkin with a cupped appearance, asshown in FIG. 3, which is advantageous for fit and leakage security. Ata width b of the front portion 6 which is between 80 and 100 mm, thecurvature of the front portion 6 should not be larger than that amaximum deviation h, front a straight transverse line between the sideedges 9, 10 of the sanitary napkin, does not exceed approx. 10 mm in thevicinity of the front edge 11.

Consequently, the front portion 6 of the sanitary napkin is angled in adirection towards the liquid-pervious cover layer 2, which implies thatthe front portion 6 is raised in the direction of the view, when thesanitary napkin is viewed with the liquid pervious cover layer 2 facingthe viewer. Furthermore, the front portion 6 is advantageously curvedalong the longitudinal centre line 23 of the sanitary napkin, in such away that the front portion 6 is bowl-shaped as seen from theliquid-pervious cover layer 2. However, the bowl-shape should not bemore pronounced than that the longitudinal centre line deviates at themost 5 mm from a straight line extending along the cnetre line betweenthe transverse folding line 22 and the front edge 11. A particularadvantage with the cupped front portion is that it further increases thestability and the deformation resistance of the sanitary napkin. Bymeans of the angle and the bowl-shape, the resistance to compression ofthe crotch portion 8 of the sanitary napkin is consequently increased.

It is advantageous if the angle of the front portion of the sanitarynapkin, in an upward direction from the liquid-pervious cover layer 2,is permanent during use. This is achieved by making the stiffeningelement 15 of a material with a stiffness which in this context is to beconsidered as very high. For reasons of comfort, it is thereforenecessary that the part of the stiffening element 15 which during use isintended to be applied in the groin area of the user is not so wide thatis causes discomfort to the user. It is therefore essential that thewidth of the sanitary napkin does not exceed the critical value whichcan be tolerated by the users. For the sanitary napkin 1 shown in FIG. 1this implies that the width of the flat portion 17 of the stiffeningelement 15 should not be larger than approx. 35 mm in an uncompressedcondition. Even if the width of the crotch portion 6 of the sanitarynapkin in tis entirety exceeds 35 mm this is, however, not critical,since the soft edge regions 18 around the stiffening element 15 permitcertain compression and adaptation of the width of the sanitary napkin 1according to the width of the groin of the user, whereby the width ofthe sanitary napkin after compressing does not exceed approx. 40 mm.

Furthermore, the material in the stiffening element 19 may be selectedso that the stiffening element itself permits a certain compressiontransversely within the crotch portion 8. In order to achievesufficiently high shape stability in the crotch portion 8, thestiffening element must, however, be sufficiently stiff to resist beingcompressed to more than 80% of its original width during normalconditions of use.

In the case that the stiffening element 19 is constituted by anextremely stiff material such as a, during normal conditions of use,totally inelastic plastic piece of material, or metal plate, it isespecially important to adapt the width of the stiffening element 19 tothe critical width of the groin of the user. When a completely inelasticstiffening element 19 is used, this should consequently not have a widthwhich exceeds approx. 30 mm.

The sanitary napkin 101 shown in FIGS. 4, 5 and 6, comprises aliquid-pervious cover layer 102, and a liquid-impervious cover layer103, which together enclose an absorbent body 104. The liquid-perviouscover layer 102 is, as in the sanitary napkin 1 shown in FIGS. 1, 2 and3, constituted by a soft, flexible, skin-friendly material. Theliquid-impervious cover layer 103, however, is constituted by a rigidmaterial, preferably a comparatively thin, stiff plastic layer, whichforms a hard, shape-retaining shell in which the absorbent body 104 isplaced.

The sanitary napkin 101 is designed with a front portion 106 which iswider than a rear portion 107, and with a crotch portion 108 which isnarrower then both the front portion and the rear portion. Due to thehigh stiffness of the liquid-impervious cover layer 103, it is essentialthat the sanitary napkin has a shape which, to a very high degree, isadapted to the anatomy of the user. Thereby, it is of particularly greatimportance that the width of the sanitary napkin, at least within thecritical area of the crotch portion 108, does not exceed approx. 40 mm.As mentioned earlier, the critical area constitutes the part of thesanitary napkin which during use is intended to be arranged between thepace-limiting muscle groups which extend down on both sides in thecrotch of the user. This area constitutes approx. 5 to 15 mm of thelength of the crotch area 108.

Furthermore, the sanitary napkin 101 exhibits two longitudinal sideedges 109, 110, a transverse concavely curved front edge 111 and atransverse convexly curved rear edge 112. The sanitary napkin isdesigned in such a way that, in the front part of the crotch portion 108there is a cross-sectional line 124 extending, in the transversedirection of the sanitary napkin, which line intersects the side edges109, 110 of the sanitary napkin. At the cross-sectional line 124, theside edges 109, 110 change inclination in relation to the longitudinalcentre line 123, whereby the width of the sanitary napkin increases in adirection towards the front edge 111, whereby the front portion 106exhibits a maximum width, which exceeds the width of the crotch portion108 at the cross-sectional line 124. Thereby, the maximum width of thefront portion 106 is preferably at least twice the width of the crotchportion 108 at the cross-sectional line 124. The inclination of the sideedges 109, 110 at the front portion 106 is defined by an angle β betweeneach respective side edge 109, 110 and a longitudinal line parallel tothe centre line 123, whereby β is between 30° and 90° and whereby thewidth of the crotch portion 108 at the cross-sectional line 124 isbetween 15 and 45 mm and preferably between 20 and 40 mm. If, however,the sanitary napkin has a construction similar to the one which is shownin FIG. 1, the width of the sanitary napkin may be allowed to be up to60 mm.

The absorbent body 104 comprises a first portion 104′, which forms alongitudinal hump 113 on the side of the sanitary napkin which is use isintended to be facing a user. The first portion 104′ consists ofmaterial with high absorption capacity, for instance absorbent fibressuch as cellulose fluff pulp, rayon or the like, with or withoutsuper-absorbent material, absorbent foam or any of the above-describedabsorbent fibre materials. Furthermore, all conceivable types ofmixtures and combinations of material layers may be used.

The absorbent body 104 of the sanitary napkin further comprises anabsorption layer 104″, arranged between the hump 113 and theliquid-impervious cover layer. The absorption layer 104″ may consist ofan absorbent nonwoven material, tissue layer or any one of theabove-mentioned absorbent materials and may, depending on the intendeduse of the sanitary napkin, be designed with larger or smallerabsorption capacity.

In the sanitary napkin shown in FIGS. 4-6, the shape of the sanitarynapkin is maintained by means of the entire liquid-impervious coverlayer 103 constituting a shape-retaining shell for the absorbent body104 of the sanitary napkin. As in the sanitary napkin in FIGS. 1-3, thefront portion 106 of the sanitary napkin 101, shown in FIGS. 4-6, isangled in relation to the crotch portion 108 of the sanitary napkin. Theangle α between the front portion 106 and the crotch portion 108 has inFIG. 5 been indicated as the angle between the inclination of the hump,along the longitudinal centre line 123 of the sanitary napkin, and theinclination of the front portion 106, since it is this inner angle whichdecides how well the sanitary napkin conforms to the shape of the bodyof the user in the relevant area. The upward bending of the frontportion 106 in relation to the crotch portion 108 does not take placealong a sharp folding line, but presents a continuous curvature in thelongitudinal direction of the sanitary napkin. Thereby, the frontportion 106 forms a softly rounded bowl which conforms very well to theanatomy of the user.

When estimating the angle α, the curvature of the front portion 106 isdisregarded so that the inclination of the front portion is determinedin relation to a straight line which extends along the longitudinalcentre line 123, from an imaginary transverse border line between thefront portion 106 and the crotch portion 108, to the front edge 111.Thereby, the exact value of the inclination of the front portion 106 inrelation to the crotch portion is not critical, but the angle α shouldbe between 20° and 50°. It is, however, advantageous if the angle α ismaintained during use, both when the article is dry, and when it hasbeen wetted by body fluid.

In FIG. 6, a cross-section through the sanitary napkin 101, shown inFIGS. 4 and 5, is shown. As is clearly evident from FIG. 6, the sideedges 109, 110 of the sanitary napkin are curved in a directiondownwardly-inwardly, as seen from the liquid-pervious cover layer 102.This implies that the sanitary napkin, along the side edges 109, 110,exhibits rounded ridges 125, 126 which during use of the sanitary napkinare intended to be in contact with the body of the user, in the groinfolds of the user. The rounded ridges 125, 126 extend along the sideedges 109, 110, along substantially the entire length of the sanitarynapkin, but flatten out somewhat at the front edge 111 and the rear edge112, respectively. Between the ridges 125, 126 and the hump 113, loweredfurrows 127, 128 extend in which menstruation exudate maybe temporarilycollected if it is not immediately absorbed into the absorbent body104′.

According to a not shown embodiment, the furrows may be made deeper byproviding the rigid liquid-impervious layer 103 with furrows. In such anembodiment, the longitudinal stiffness of the sanitary napkin isincreased, at the same time as it becomes easier to compress the crotchportion. Accordingly, beams in the form of ridges and furrows increasethe stiffness in the extension direction of the beams while, on theother hand, the stiffness in the perpendicular direction is reduced.

The raised ridges 125, 126, along the side edges 109, 110 of thesanitary napkin, fulfil several functions. On one hand, they constitutereinforcement beams which increase the bending resistance of thesanitary napkin when bending along substantially transverse bendinglines, and on the other hand, the rounded surface which faces the usercontributes to increase user comfort. Furthermore, the shaping of thestiff, liquid-impervious cover results in a certain degree ofcompressibility during use. Thereby, the raised ridges and thelongitudinal ledges of the central hump 113 serve as notches, wherebycompression of the crotch portion 108 may take place in a controlledmanner. During use of the sanitary napkin, pressure forces from thethighs and groin of the user have the effect that the side edges 109,110 of the sanitary napkin are pressed inwards in a direction towardsthe longitudinal centre line 123. What happens then is that the raisedridges 125, 126 are curved slightly inwards in a direction towards thehump 113. Consequently, the crotch portion 108 of the sanitary napkingenerally maintains the shape it has been given in the production, evenif the width of the crotch portion is slightly reduced by compression. Aparticular advantage is that no undesired further creasing, or otherundesired deformation, of the crotch portion 108 takes place.

When liquid-impervious cover layers of, for example, polyethyleneplastic or polypropylene plastic with a thickness of between approx. 0,5mm and 1 mm are used, the formed crotch portion 108 exhibits highresiliency. Consequently, the crotch portion 108 substantially recoversits original shape and width so that the compression is discontinued. Asin the sanitary napkin shown in FIGS. 1-3 it is, however, essential thatthe crotch portion always has a guaranteed minimum width during use, inorder to avoid leakage. For this reason, the stiffness of the crotchportion must be sufficiently high that it is not compressed to more thanapprox. 80% of its original width during normal conditions of use.

In order to further increase the comfort for the user, the front portion106 is provided with a recess at the front edge 111. The recess isformed by means of the front edge 111 being curved in a directiontowards the crotch portion 108 of the sanitary napkin. Since the frontedge 108 is concavely curved, it conforms to the outline of the monsveneris of the user in a better way, whereby the risk of chafing isalmost non-existent.

EXAMPLE 1

In order to estimate the edge stiffness of an absorbent article, i.e.the resiliency of the article when it is subjected to compression in atransverse direction, the following test was performed:

The absorbent article was divided into two halves along the longitudinalcentre line, whereafter one of the halves was clamped between two jawsmounted in an Instron tensile tester (1122, 4301, or 44664 with a 10 Ncell) whereby the cut edge of the article was directed downwards betweenthe jaws with the intact side edge freely protruding from the jaws.Thereafter, a metal rod having a cylinder mounted thereon was pressedperpendicularly against the edge at the region of the article whichduring use is arranged in the critical area in the crotch of the user.The force which was required in order to press down the edge wasrecorded by means of the tensile tester as a function of thedown-pressed distance. The cylinder which was used to press against theedge was 40 mm long and had a diameter of 10 mm.

When the metal rod is pressed against the edge of the article an initialresistance arises. This is very distinct in the case of homogenous stiffmaterials such as plastic or hard paper. In the case of thicker, porousor fibrous materials, the edge splinters before it bends or cracks. Twoforce peaks are recorded for such materials.

As absorbent article such as a sanitary napkin, an incontinence guard,or a panty-liner may exhibit several stiff edges and consequently givesrise to several force peaks. The article may, for example, first have awelded edge joint, then a relatively soft and wide first absorbent coreand thereafter a narrower, harder absorbent core. Absorbent articleswith a shell, or a stiffening element of a resilient material such as abent plastic layer, do not give rise to a distant force peak; instead,the impression force is almost proportional to the distance which themetal rod with the cylinder has been impressed.

In order for an absorbent article to have a sufficiently high resistanceto transverse compression, it should not be possible during normalconditions of use to compress the crotch portion of the article morethan that the width of the article is always at least approx. 15 mm andpreferably is always at least approx. 20 mm. Furthermore, articles witha width which to begin with exceeds 40 mm should be easily compressed bymeans of the action of the forces which arise during use, so that thewidth during use does not exceed approx. 40 mm.

It proved to be difficult to exactly specify a force at which anabsorbent article could be presumed to exhibit sufficient shapepermanence. In order to estimate the magnitude of the force it must betaken into consideration that the recorded force varies depending on theabove-mentioned factors, and also that it is difficult to accuratelypredict the force action which the article will be subjected to duringuse. The performed edge stiffness measurements, however, indicated thatthe force which is required to press the side edge of the articleinwards a distance of 10 mm should be greater than approx. 20 N if anabsorbent article according to the invention is to be regarded as havingsufficient shape permanence.

For very stiff articles, for example with stiffening elements of metal,a measurement of the edge stiffness of course becomes meaningless.Accordingly, the method is primarily suited to determining whether anabsorbent article has sufficient resistance to compression.

Materials such as paper, or heavily compressed fibre layers, which breakwhen compressed so that they thereafter lose their ability to resistcompression cannot be used of articles according to the invention.

EXAMPLE 2

The intrinsic stiffness of a number of flat materials was determined bymeans of the ASTM D 4032-82 Circular Bend Procedure, which method isdescribed in detail in EP 0 336 578. The equipment consists of arectangular plate which in the middle has a circular, funnel-shapedopening. The material is placed above the circular opening and issubjected to a force so that the material reaches down to the bottom ofthe plate. The force is measured and provides a value for the intrinsicstiffness of the material.

The materials which were found to have an intrinsic stiffness suitablefor the purpose of the invention were materials for which a force of atleast 100 N was recorded.

The invention should not be regarded as being limited to the hereindescribed embodiments, but a number of further variants andmodifications are conceivable within the scope of the claims. Forinstance, the invention comprises all types of absorbent articles whichsubstantially are accommodated in the groin area of a user. Furthermore,all conceivable combinations of the descried embodiments are intended tobe embraced by the invention.

What is claimed is:
 1. Absorbent article which article has a generallyelongated shape with a longitudinal direction and a transverse directionand exhibits two side edges, two end edges, two end portions and acrotch portion located between the end portions, which articlefurthermore exhibits a liquid-pervious cover layer, intended to befacing the user when worn, and a liquid-impervious cover layer, intendedto be facing away from the user when worn, wherein the article at leastwithin the crotch portion comprises a stiffening element of a materialwith a very high intrinsic stiffness so as to maintain substantial shapepermanence of the article while worn by a user, whereby within at leasta 5 mm extension of the crotch portion in the longitudinal direction,the article has an extension in the transverse direction which isbetween 15 mm and 40 mm while the article is worn by a user. 2.Absorbent article according to claim 1, wherein the stiffening elementmay only be compressed to approx. 80% of its original width duringcompression of the crotch portion in the transverse direction of thearticle with forces which occur while the article is worn by a user. 3.Absorbent article according to claim 1, wherein the stiffening elementis profiled in the transverse direction of the article and exhibits atleast one ridge, or furrow extending in the longitudinal direction. 4.Absorbent article according to claim 3, wherein a longitudinal ridgewith a rounded surface is arranged along each side edge of the articleat least line the crotch portion.
 5. Absorbent article according toclaim 1, wherein the stiffening element in the crotch portion on bothsides of the stiffening element along the side edges of the article issurrounded by soft, easily deformable edge portions.
 6. Absorbentarticle according to claim 1, wherein a force of at least 20 N isrequired in order to press one of the side edges of the article inwardsa distance of 10 mm during compression perpendicularly to said one ofthe side edges.
 7. Absorbent article according to claim 1, wherein theend portions are constituted by a front portion and a rear portion,wherein the article at least within the front portion and the crotchportion exhibits high bending resistance against bending alongtransversely extending bending lines, whereby the front portion and thecrotch portion of the article exhibit high shape permanence while thearticle is worn by a user, and also that the front portion of thearticle is inclined in relation to the crotch portion, in a directiontowards the liquid-pervious surface, whereby the front portion forms anangle α towards the crotch portion.
 8. Absorbent article according toclaim 7, wherein the article at least within the front portion and thecrotch portion exhibit high bending resistance against bending alonglongitudinally extending bending lines.
 9. Absorbent article accordingto claim 1, wherein the crotch portion of the article exhibits atransversely extending cross-sectional line, wherein the side edges ofthe article change inclination in relation to the longitudinal centreline of the article in the vicinity of the points of intersectionbetween the cross-sectional line and the side edge, and from whichcross-sectional line the width of the article increases in a directiontowards the front edge, whereby the front portion exhibits a maximumwidth, which exceeds the width of the crotch portion at thecross-sectional line, wherein the tapered inclination of the side edgesat the front portion is defined by means of an angle β between eachrespective side edge and a longitudinal line parallel to the centreline, wherein β is between 10° and 90°.
 10. Absorbent article accordingto claim 1, wherein the liquid-impervious cover layer of the article isconstituted by a liquid-impervious, stiff plastic layer whereby theliquid-impervious cover layer constitutes the stiffening member of thearticle.
 11. Absorbent article according to claim 1, wherein theabsorbent article is a sanitary napkin, an incontinence guard, or apanty-liner.
 12. Absorbent article according to claim 1, wherein thearticle has an extension in the transverse direction which is between 20mm and 35 mm while the article is worn by a user.
 13. Absorbent article,which has a generally elongated shape with a longitudinal direction anda transverse direction and exhibits two side edges, two end edges, twoend portions, and a crotch portion located between the end portions,which article furthermore exhibits a liquid-pervious cover layer,intended to be facing the user when worn, and a liquid-impervious coverlayer, intended to be facing away from the user when worn, wherein thearticle at least within the crotch portion comprises a stiffeningelement of a material with an intrinsic stiffness of at least about 100N.
 14. Absorbent article, which has a generally elongated shape with alongitudinal direction and a transverse direction and exhibits two sideedges, two end edges, two end portions, and a crotch portion locatedbetween the end portions, which article furthermore exhibits aliquid-pervious cover layer, intended to be facing the user when worn,and a liquid-pervious cover layer, intended to be facing away from theuser when worn, wherein the article at least within the crotch portioncomprises a stiffening element of a material with an intrinsic stiffnessof at least about 100 N, whereby within at least a 5 mm extension of thecrotch portion in the longitudinal direction, the article has anextension in the transverse direction which is between 15 mm and 40 mmwhile the article is worn by a user.
 15. Absorbent article, whicharticle has a generally elongated shape with a longitudinal directionand a transverse direction and exhibits two side edges, two end edges,two end portions, and a crotch portion located between the end portions,which article furthermore exhibits a liquid-pervious conver layer,intended to be facing the user when worn, and a liquid-impervious coverlayer, intended to be facing away from the user when worn, wherein thearticle at least within the crotch portion comprises a stiffeningelement of a material with a very high intrinsic stiffness so as tomaintain sufficiently high shape stability of the article while worn bya user, whereby within at least a 5 mm extension of the crotch portionin the longitudinal direction, the article has an extension in thetransverse direction which is between 15 mm and 40 mm while the articleis worn by a user.
 16. Absorbent article according to claim 15, whereinthe stiffening element may only be compressed to approx. 80% of itsoriginal width during compression of the crotch portion in thetransverse direction of the article with forces which occur while thearticle is worn by a user.